Tomography generally denotes an imaging medical slice recording method that enables the production of three-dimensional image information relating to a body region of a patient that is to be examined. In this sense, the term tomography includes computed tomography, in particular, but also magnetic resonance (MR) tomography.
Computed tomography on the one hand, and MR tomography on the other hand, resemble one another—irrespective of the different measurement principle—to the effect that firstly a raw data record of the body region of the patient that is to be examined is firstly recorded, and the desired three-dimensional image information is calculated therefrom only later by applying mathematical algorithms. This calculation step is denoted below as 3D reconstruction.
Computed tomography and MR tomography are also similar to one another in that the image quality of the image (or tomogram) calculated by way of 3D reconstruction is a function of a multiplicity of acquisition parameters of the respective tomography device. In the case of computed tomography, the acquisition parameters particularly include technical parameters such as the tube voltage and the tube current of the X-ray tube, the table feed speed, the tube rotation time, the collimation, etc. In the wider sense, the acquisition parameters are taken below also to include variables that characterize the image processing, in particular the image reconstruction. Thus, the acquisition parameters of the latter type chiefly include the parameters of the 3D reconstruction algorithm, in particular the slice thickness and the increment.
Because of the multiplicity of the acquisition parameters and the sometimes complex interaction between various acquisition parameters, the user of a tomography device requires considerable experience in order to find a favorable configuration of the acquisition parameters straight away with regard to a specific examination to be undertaken and to a specific patient. On the one hand, an unfavorable parameter configuration can result in a low, sometimes even inadequate image quality that, in the extreme case, can even necessitate repeating the examination. On the other hand, parameters can be selected that are associated with a comparatively high dose but, with reference to the targeted examination, are associated as a rule with no, or only a slight gain in information by comparison with a standard image quality. Both cases result in an unnecessary, since additional burden, in particular radiation burden, for the patient, an additional loading of the medical device and an unnecessary loss of time.
Modern tomography devices frequently offer a multiplicity of different protocols with stipulations for the setting of the acquisition parameters, in order to alleviate the complex parameter setting for the user. However, these protocols generally have to be adapted manually to the specific problem and/or the patient profile (body size, weight, . . . ). Again, in modern computer tomographs the tube current is matched to the patient profile in a semi-automated fashion.
Particularly for the examination of children, the provision of such protocols has, however, so far led at best to a comparatively slight alleviation, even more so as precisely with children the setting of the acquisition parameters that is “optimal” for a specific problem can vary substantially as a function of growth and development. On the other hand, there is frequently a certain deficit of experience precisely in the case of the tomographic examination of children. On the one hand, the operating staff of a tomography device, in particular a radiologist entrusted with a computer tomograph, frequently has only a comparatively slight specialized knowledge of the particular requirements for the tomographic examination of children. On the other hand, in turn, specialized child radiologists frequently have no continuous access to a tomography device, and can therefore obtain only limited experience of the particular unit.
It is proposed in DE 101 60 611 A1, for the purpose of a simplified setting of acquisition parameters of an imaging medical examination unit, to undertake the acquisition parameters in the generic sense indirectly by selecting a stored exemplary image originating from an earlier examination. Here, the exemplary image is modified by changing the contrast and the brightness in order to simulate various parameter settings of equipment parameters. When an image modified in such a way is selected, the simulated parameter settings are taken over as actual equipment settings.
The known method is provided in general for use with imaging medical methods, but in particular is set up and suitable for two-dimensional X-ray photographic methods. In these X-ray photographic methods, an unfavorable parameter selection leads to an “underexposure” or “overexposure” that can be simulated by varying contrast and brightness of the exemplary image. By contrast, the known method is little suited to simulating the parameter settings in the case of a tomography device.